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At least 19 recordsLinked to original sources
PubMed1992

Role of ceramic implants. Design and clinical success with total hip prosthetic ceramic-to-ceramic bearings.

Ceramic implants have become of great interest because of the increased awareness that wear debris from metal-polyethylene components of total hip prostheses can cause osteolysis around implants. Polyethylene wear rates with the Charnley total hip prosthesis were found to be from 0.1 to 0.2 mm/year in the elderly, which corresponded to 30 to 80 mm3 of polyethylene debris being released to the joint tissues. This in turn can be related to 40 million to 40 billion particles being released into the joint every year. This polyethylene particulate is heavily implicated in the osteolytic destruction of periarticular tissues. The ceramic ball, ceramic cup combination of total hip prostheses may have promise of wear rates that could be thousands of times smaller than polyethylene alone. Such alumina ceramic prosthetic concepts were introduced in Europe from 1970 to 1973. Under Food and Drug Administration regulations at that time, the only U.S. introductions allowed circa 1980 were the Autophor and Xenophor types of ceramic prostheses. However, this particular prosthetic design was not successful in the United States because of pain, neck-socket impingement, ceramic fracture, and component loosening. This did not therefore appear to be a successful compromise in the hands of U.S. surgeons. Ceramic innovations from Europe now include cemented ceramic cups of "matching" tolerances with the femoral ball, and press-fit Ti-alloy acetabular shells with modular ceramic inserts. In addition, alumina and zirconia ceramic balls are now in routine clinical use in Europe. The objectives of this Symposium are to highlight these ceramic ball, ceramic cup innovations with their long-term clinical results from Europe. Then one can evaluate which of these innovations in material and design selections offers the best possible alternatives in the 1990s.

Alloys↗
PubMed1992

Differences in ceramic-bone interface between surface-active ceramics and resorbable ceramics: a study by scanning and transmission electron microscopy.

The interface between bioactive ceramics and bone was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The materials were apatite-wollastonite-containing glass ceramic (A-W.GC) as a representative surface-active ceramic, and calcite and beta-tricalcium phosphate (beta-TCP) as resorbable ceramics. Particles of these materials, ranging between about 100 microns and 300 microns in diameter, were implanted into rat tibiae, and specimens were prepared for observation at 8 weeks after implantation. Both SEM and TEM demonstrated that A-W.GC was bonded to bone through a thin Ca-P-rich layer consisting of fine apatite crystals apparently different from those of bone in shape, size, and orientation. Collagen fibers of the bone reached the surface of this layer, and chemical bonding between A-W.GC and the bone was speculated. Calcite and beta-TCP, on the other hand, made direct contact with the bone, and no apatite layer was present at the interface. The surfaces of the implants became rough due to degradation, and bone grew into the finest surface irregularities. However, we were unable to demonstrate any continuity of crystals between the resorbable implants and bone by high-resolution TEM. Accordingly, the bonding strength was considered to be mainly attributable to mechanical interlocking.

Animals↗
PubMed1977

[Comparative experimental investigations with bioglass (L. L. Hench), Al2O3-ceramic and Al2O3-ceramic coated with a mod. Bioglass. I. Results of experiments under non-loaded conditions (author's transl)].

This report deals with comparative results obtained with unloaded intra-osseous implants of bioglass (L. L. Hench), Al2O3-ceramic and Al2O3-ceramic coated with a mod. bioglass. Al2O3-ceramic and bone form a direct bony interface without fibrous tissue interposition, this resulting in a pure mechanic fixation of the implant through frictional forces of the surface roughed ceramic. Pure bioglass (45S5) and bone form a unique persisting direct interface by means of physico-chemical or biochemical phaenomena stabilizing the implant. Interface stability seams to be higher than the fatique strenth of the glass itself. This interface is developed as a consequence of solubility of some of the glass constituents within a surface layer of up to 200 microns, running parallel with a reduction of strength of this surface glass layer. The boronoxide containing bioglass, flame-sprayed onto Al2O3-ceramic samples seams to be less soluble and therefore seams to have lesser bonding capability to bone. The stability of the interface bioglass coating-Al2O3-ceramic was low.

Aluminum↗
PubMedDate not supplied

[The clinical evaluation of the use of metal ceramic dentures with a Simet glass-ceramic coating].

Good results of clinical follow-up of patients with cermet dentures coated with cimet (glass ceramic) permit recommending this type of coating for wide practical use. Reconstructive prosthetics with glass ceramic and metal and cermet dentures should involve denture modeling in the articulator and a prophylactic check-up at least once a year with oral hygiene and functional occlusion control.

Adult↗
PubMedDate not supplied

The effect of venting on the strength of Dicor and Hi-Ceram ceramic crowns.

Research has shown that external venting improves the marginal fit of cast crowns by decreasing hydrostatic pressure during seating. In turn, improving marginal fit has been shown to increase the strength of castable glass and other porcelain systems. This study evaluated the effect on the compressive strength of crowns with vent holes placed during and after fabrication. Forty-five artificial crowns were made from each material and divided into three equal groups: (1) crowns without vent holes, (2) crowns with a vent hole placed before casting, and (3) crowns with a vent hole placed using a rotary diamond instrument after casting. Standardized crowns were acid etched, silane treated, and filled with epoxy resin to provide a support base for testing. The crowns were then loaded to failure. One-way analysis of variance showed a significant difference among groups. Scheffe's Multiple Comparison Test was used for discrimination. The Dicor unaltered and fabricated vent group and the Hi-Ceram unaltered group had significantly higher resistance to fracture.

Aluminum Oxide↗
PubMed1992

Ten-year survivorship of cemented ceramic-ceramic total hip prosthesis.

In the first 187 consecutive alumina-alumina combination hip arthroplasties performed from 1977 to 1979, both components were cemented with conventional techniques. At ten-year follow-up evaluation, 87 patients were reviewed or interviewed by telephone, 37 were dead, 39 were lost to follow-up evaluation, and 24 failures were reoperated on before the end of ten years. The major cause of failure was aseptic loosening of the acetabular component (15 failures). Fracture of the socket and of the femoral head occurred in five patients in this series. However, these complications were not seen with components manufactured after 1979. At the end of ten years, survivorship analysis depicted a 82.59% survival rate when reoperation was considered as failure and a 88.57% rate when reoperation for aseptic loosening was considered as failure. The femoral component had a 99.16% survival rate and the acetabular component had an 88.57% survival rate when reoperation for aseptic loosening was considered as failure. Age, appearance of a two- or three-zone demarcation at the intermediate follow-up evaluation, and outer diameter of the acetabular component were the major parameters influencing the results. Better results observed in the population younger than 50 years of age may be related to the small amount of wear debris produced by the alumina-alumina combination. This combination in hip prosthesis is secure, but should be implanted in young and active patients; the outer diameter of the acetabular component must be at least 50 mm. The major problem that remains is the socket's fixation. It could be improved by a design modification, by choosing another mode of fixation, or both.

Aluminum Oxide↗
PubMed1992

Osteogenesis in marrow-derived mesenchymal cell porous ceramic composites transplanted subcutaneously: effect of fibronectin and laminin on cell retention and rate of osteogenic expression.

Cultured-expanded rat marrow-derived mesenchymal cells differentiate into osteoblasts when combined with a porous calcium phosphate delivery vehicle and subsequently implanted in vivo. In this study, the effects of ceramic pretreatment with the cell-binding proteins fibronectin and laminin on the osteogenic expression of marrow-derived mesenchymal cells were assessed by scanning electron microscopy, [3H]-thymidine-labeled cell quantitation, and histological evaluation of bone formation. Scanning electron microscopic observations showed that marrow-derived mesenchymal cells rapidly spread and attach to both fibronectin- or laminin-adsorbed ceramic surfaces but retain a rounded morphology on untreated ceramic surfaces. Quantitation of [3H]-thymidine labeled cells demonstrated that laminin and fibronectin preadsorbed ceramics retain approximately double the number of marrow-derived mesenchymal cells than do untreated ceramics harvested 1 wk postimplantation. Histological observations indicate that the amount of time required to first detect osteogenesis was shortened significantly by pretreatment of the ceramic with either fibronectin or laminin. Fibronectin- and laminin-coated ceramic composite samples were observed to contain bone within 2 wk postimplantation, while in untreated ceramic the earliest observation of bone was at 4 wk postimplantation. A comparison was made of the initial cell-loading, in vivo cell retention characteristics, and rate of osteogenesis initiation of marrow-derived mesenchymal cells on two types of ceramic with different pore structure and chemical composition, with and without preadsorption with fibronectin or laminin. "Biphasic" ceramics contain randomly distributed pores 200-400 microns in diameter, and "coral-based" ceramics have continuous pores of approximately 200 microns in diameter. Laminin or fibronectin preadsorption significantly increases the number of cells retained in all ceramic test groups by day 7 postimplantation. In addition, by day 7 postimplantation, the biphasic ceramics retain a significantly greater number of cells for all test groups than do coral-based ceramics. The biphasic ceramics consistently have more specimens positive for bone with the identical cell-loading conditions used throughout this study. These results indicate that the retention of cells within the ceramic is an important factor for optimization of marrow mesenchymal cell initiated bone formation. The retention of cells within ceramics is augmented by the adsorption of the cell-binding proteins laminin and fibronectin, but this effect varies depending on ceramic pore structure and/or chemical composition.

Animals↗
PubMed1979

[Experimental study on an artificial hip joint made of Al2O3 ceramics (author's transl)].

For the purpose of developing the ceramic artificial hip joint, we carried out biological and mechanical experiments. Tiny blocks of polycrystalline ceramic were inserted into the femurs of rabbits. Also, ceramic powder was injected into the knee joints of rabbits. Biological reaction were examined after varying intervals. It was proved, as a result, that ceramics have good affinity with living tissue. As a next step, wedge-shaped test pieces were inserted into the distal end of the femurs of dogs and tensile tests were carried out to investigate the degree of fixation of ceramic with bone. The result was that ceramic test pieces showed firmer fixation than those of metal. In the hip joints of five dogs, ceramic total hip prostheses for dogs were implanted. The dogs were autopsied after varying intervals and investigated histopathologically and scanning electron microscopically. Fixation of the socket and the prosthesis with the bone was superior to those made of metal and, moreover, virtually no wearing had taken place. However, the socket or prosthetic stems in four dogs were observed damaged in some parts. From the above mentioned, it is evident that when making ceramic total hip prostheses, we have to select ceramics of good quality and thicken their weightconcentrated parts by a device of its own design or use partly metal components coated with ceramic.

Acetabulum↗
PubMed1992

A review of the strength properties of dental ceramics.

New ceramic materials for restorative dentistry have been developed and introduced in recent years. This article reviews advantages and disadvantages of dental ceramics, concentrating on strength properties. Included are factors affecting the strength of dental ceramic materials and the most common mechanisms for increasing the strength of dental ceramics. The properties of presently available materials such as dispersion-strengthened ceramics, cast ceramics, and foil-reinforced materials are discussed. Current research efforts to improve the fracture resistance of ceramic restorative materials are reviewed. A description of methods to evaluate the strength of ceramics is included, as a caution concerning the interpretation of strength data reported in the literature.

Ceramics↗
PubMed1976

[Studies on the application of apatite to dental materials. (I) --Apatite ceramics-- (author's transl)].

Apatite ceramics is composed of hydroxyapatite [Ca10(PO4)6(OH)2] sintered at high temperature. It is known that hydroxyapatite is the main component of bone and tooth minerals. There are two synthetic methods for the apatite powder. One is so called wet synthetic method: Synthesis by the reaction of Ca++ and PO4--- in the aqueous solution of approximately pH 7.0, the other is dry method: Synthesis by the solid state reaction at high temperature. The apatite powder stable below 1400 degrees C was prepared by the latter method in this work. After passing through a sieve, this powder was cold-pressed and then sintered at 1000 degrees C to 1300 degrees C in air. Biological apatite powders were also perpared as a reference. It was found that any apatite ceramics having porosity in the range of 5 to 50% could be obtained under the various sintering conditions. Compressive strength of these apatite ceramics increased with the reduction of the porosity, and those with porosity less than 20% were more than 100 kg/cm2. Vickers hardness was measured. This result showed the same tendency as that of compressibility. Hardness of the apatite ceramics with 90% relative density was almost the same or more as that of enamel. Solubility of the synthetic apatite powder in distilled water and aqueous solution of lactic acid (pH 4.0) was nearly the same as biological apatites. The dissolution rate decreased with the reduction of porosity of the ceramics. It was certified that hot pressing technique was extremely effective to obtain high density ceramics (more than 95% of density) and thus low parosity apatite ceramics. From the facts as described above, it is understood that sintered pure hydroxy-apatite is an excellent ceramics of high mechanical strength.

Apatites↗